Re: [Qemu-devel] [PATCH for-1.6] virtio: clear signalled_used_valid when switching from dataplane

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Aug 12, 2013 at 11:08:09AM +0200, Stefan Hajnoczi wrote:
> When the dataplane thread stops, its vring.c implementation synchronizes
> vring state back to virtio.c so we can continue emulating the virtio
> device.
> 
> This patch ensures that virtio.c's signalled_used_valid flag is reset so
> that we do not suppress guest notifications due to stale signalled_used
> values.
> 
> Suggested-by: Kevin Wolf <kwolf@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Good point

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

and we also need this for vhost.c right?

> ---
>  hw/virtio/dataplane/vring.c | 1 +
>  hw/virtio/virtio.c          | 5 +++++
>  include/hw/virtio/virtio.h  | 1 +
>  3 files changed, 7 insertions(+)
> 
> diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c
> index 82cc151..351a343 100644
> --- a/hw/virtio/dataplane/vring.c
> +++ b/hw/virtio/dataplane/vring.c
> @@ -52,6 +52,7 @@ bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
>  void vring_teardown(Vring *vring, VirtIODevice *vdev, int n)
>  {
>      virtio_queue_set_last_avail_idx(vdev, n, vring->last_avail_idx);
> +    virtio_queue_invalidate_signalled_used(vdev, n);
>  
>      hostmem_finalize(&vring->hostmem);
>  }
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 09f62c6..706bdf4 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -1059,6 +1059,11 @@ void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx)
>      vdev->vq[n].last_avail_idx = idx;
>  }
>  
> +void virtio_queue_invalidate_signalled_used(VirtIODevice *vdev, int n)
> +{
> +    vdev->vq[n].signalled_used_valid = false;
> +}
> +
>  VirtQueue *virtio_get_queue(VirtIODevice *vdev, int n)
>  {
>      return vdev->vq + n;
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index d7e9e0f..a90522d 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -237,6 +237,7 @@ hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n);
>  hwaddr virtio_queue_get_ring_size(VirtIODevice *vdev, int n);
>  uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n);
>  void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx);
> +void virtio_queue_invalidate_signalled_used(VirtIODevice *vdev, int n);
>  VirtQueue *virtio_get_queue(VirtIODevice *vdev, int n);
>  uint16_t virtio_get_queue_index(VirtQueue *vq);
>  int virtio_queue_get_id(VirtQueue *vq);
> -- 
> 1.8.3.1